lkml.org 
[lkml]   [2018]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[V9fs-developer] [PATCH v2] net/9p: Fix a deadlock case in the virtio transport
Date
When client has multiple threads that issue io requests
all the time, and the server has a very good performance,
it may cause cpu is running in the irq context for a long
time because it can check virtqueue has buf in the *while*
loop.

So we should keep chan->lock in the whole loop.

Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
---
net/9p/trans_virtio.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 05006cb..e5fea8b 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -148,20 +148,15 @@ static void req_done(struct virtqueue *vq)

p9_debug(P9_DEBUG_TRANS, ": request done\n");

- while (1) {
- spin_lock_irqsave(&chan->lock, flags);
- req = virtqueue_get_buf(chan->vq, &len);
- if (req == NULL) {
- spin_unlock_irqrestore(&chan->lock, flags);
- break;
- }
- chan->ring_bufs_avail = 1;
- spin_unlock_irqrestore(&chan->lock, flags);
- /* Wakeup if anyone waiting for VirtIO ring space. */
- wake_up(chan->vc_wq);
+ spin_lock_irqsave(&chan->lock, flags);
+ while ((req = virtqueue_get_buf(chan->vq, &len)) != NULL) {
if (len)
p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
}
+ chan->ring_bufs_avail = 1;
+ spin_unlock_irqrestore(&chan->lock, flags);
+ /* Wakeup if anyone waiting for VirtIO ring space. */
+ wake_up(chan->vc_wq);
}

/**
--
1.8.3.1
\
 
 \ /
  Last update: 2018-07-17 13:05    [W:0.059 / U:0.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site